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1. Field of the Invention
This invention relates to the field of beach and shoreline renourishment. More specifically. the invention comprises a modular water-permeable fence assembly designed to impede the flow of suspended particlesxe2x80x94thereby producing sand accretion. A method for deploying the fence assembly is also disclosed.
2. Description of the Related Art
Beach and shoreline erosion is a recognized problem in many areas. Erosion and accretion are natural processes whereby shorelines advance and retreat over time. Where structures are erected on the shoreline, however, the natural erosion jeopardizes property having substantial economic worth.
Various methods have been used to impede or prevent beach erosion. It has long been known that suspending a mesh or net in the water near the beach tends to cause an accumulation of sand in the region of the net. One such device is disclosed in U.S. Pat. No. 3,564,853 to Csiszar (1969) Another approach based on the same concept is disclosed in U.S. Pat. No. 4,089,179 to Trautman (1978). Both these inventions require the deployment of supporting pilings or anchors a considerable distance offshore.
In recent years, efforts have focused on the use of fence structures arrayed in a direction perpendicular to the beach. One such fence structure is disclosed in U.S. Pat. No. 4,710,056 to Parker (1987). The Parker device uses a line of flexible mesh suspended from evenly spaced supports. The supports are actually three-legged structures, with each leg being driven or buried in the sand at an angle for added stability. While the Parker device does succeed in accumulating sand, the mesh employed tends to become buried. Both the buried mesh and the submerged portions of the support legs become exceedingly difficult to remove. The tendency of the fence structures to become submerged and stuck within the sand they accumulate is, in fact, one of the most significant recognized problems with this approach.
U.S. Pat. No. 5,255,997 to Bailey et.al. (1993) provides an excellent explanation of this self-burial phenomenon. FIG. 11 of the Bailey disclosure illustrates mesh panels capable of sliding up and down on their supporting poles. As the text explains, the panels tend to sink within the deposited material (river mud), until their downward progress is checked by restraining straps.
A device which is capable of adjusting the height of the mesh deployed is disclosed in U.S. Pat. No. 5,720,573 to Benedict et.al. (1998). As seen in FIG. 1, the Benedict device incorporates a rigid horizontal rod which spools up the mesh fabric and prevents unwanted immersion in the accumulated sand. Several versions are disclosed, including one where the height of adjacent mesh panels is adjustable somewhat independently (see FIG. 14). FIG. 15 of the Benedict disclosure shows mesh panels mounted in a rigid frame. These panels can presumably be raised and lowered with respect to the support pilings. It is important to realize, however, that the panels are subject to considerable force from wave impact. Ideally the waves travel in a direction which is perfectly perpendicular to the fence, but this is often not the case. It is therefore important to secure the fence panels to the support pilings so that the panels cannot bend and thereby escape the securing device. The arrangement shown in the ""573 disclosure obviously does not address this concern. In addition, the ""573 disclosure requires the use of bulky external brackets to the support pilings.
FIG. 17 of the ""573 disclosure is generally instructive regarding the use of fence structures, as it shows a plan view of several fence structures deployed along a shoreline. The array illustrated is typical of how these devices are used; i.e., a series of several fence structures is needed.
Accordingly, the prior art devices are limited in that they:
1. Require the deployment of pilings or support structures a considerable distance from shore;
2. Do not provide means for preventing the burial of the fence material used,
3. Are insufficiently rigid to resist wave forces; and
4. Require the addition of external brackets on the pilings.
The present invention comprises a beach renourishment sand snare and a method for its employment. A series of metal posts are embedded in the sand, forming a line which is approximately perpendicular to the shore. Each post has a pair of slots cut vertically down its side, with the slots all lining up in a direction which is perpendicular to the shore. Semi-rigid mesh panels are constructed of polymer coated wire mesh. Each side of the mesh panel is enclosed in a clamping assembly. Each clamping assembly is configured to slide into the slots cut into the posts, with means provided to secure the clamping assembly in place in the slot. Thus, a mesh panel may be lowered into place and secured between adjacent posts by sliding the clamping assemblies on either side of the mesh panel into the slots in the two adjacent posts.
A method of applying the sand snare is also disclosed. The placement of the mesh panel in the surf tends to accumulate sand around the panel. The sand will eventually accumulate to the point that the shoreline will advance seaward of the mesh panel. Because each mesh panel is independently placed, once the shoreline has advance past its position, that panel can be removed and transferred to the seaward end of the line of posts. Likewise, the posts on the landward side can be removed and transferred to the seaward side once they are no longer neededxe2x80x94thereby extending the line of posts. In this fashion, a series of posts and mesh panels can be xe2x80x9cwalkedxe2x80x9d into the sea, accumulating sand and advancing the shoreline indefinitely.